Impulsivity as a Risk Factor
for Concurrent Disorders
James MacKillop, PhD
Peter Boris Chair in Addictions Research
Director, Peter Boris Centre for Addictions Research
Professor, Department of Psychiatry and Behavioural Neurosciences
Overview
 Evolving definitions of impulsivity and self-control
 Delay discounting, a behavioral economic index of
impulsivity
 Impulsive discounting, addictive disorders and other
psychiatric disorders
 Brain imaging and clinical applications
 Future directions
Evolving Definitions of Impulsivity
and Self-Control
Impulsivity 1.0
Impulsivity
Impulsivity 2.0
Impulsivity
Sensation
Seeking
Lack of
Premeditation
Lack of
Perseverance
Negative
Urgency
Positive
Urgency
Impulsivity 3.0
Impulsivity
Impulsive
Personality
Traits
Behavioral
Inhibition
[Impulsive
Action]
Delay
Discounting
[Impulsive
Choice]
Delay Discounting, a Behavioral
Economic Index of Impulsivity
Delay Discounting
Which would you prefer?
Now
Later
Mischel et al. (1958, 1989, 1999, 2011)
Delay Discounting
Which would you prefer?
Now
Later
Mischel et al. (1958, 1989, 1999, 2011)
Delay Discounting
Which would you prefer?
Now
Later
Mischel et al. (1958, 1989, 1999, 2011)
Delay Discounting
Which would you prefer?
Now
Later
Mischel et al. (1958, 1989, 1999, 2011)
Delay Discounting
Which would you prefer?
Now
Later
Mischel et al. (1958, 1989, 1999, 2011)
Delay Discounting
Which would you prefer?
Now
Later
Mischel et al. (1958, 1989, 1999, 2011)
Delay Discounting
Which would you prefer?
Now
Later
Mischel et al. (1958, 1989, 1999, 2011)
Delay Discounting
 Behavioral economic index of impulsivity
 Delay discounting refers to the amount that a reward is
discounted based on its delay in time
 Smaller-Sooner vs. Larger-Later Preference
 Delay Discounting Task
 Would you rather have $A today or $B in C days?
 Points of indifference gathered across time periods
 Temporal Discounting Function(s):
V = A/(1 + kD)
Ainslie, 1975; Bickel & Marsh, 2000; Mazur, 1987; Rachlin & Green, 1972; Reynolds, 2006
Delay Discounting
 Behavioral economic index of impulsivity
 Delay discounting refers to the amount that a reward is
discounted based on its delay in time
 Smaller-Sooner vs. Larger-Later Preference
 Delay Discounting Task
 Would you rather have $99 today or $100 in 7 days?
 Points of indifference gathered across time periods
 Temporal Discounting Function(s):
V = A/(1 + kD)
Ainslie, 1975; Bickel & Marsh, 2000; Mazur, 1987; Rachlin & Green, 1972; Reynolds, 2006
Delay Discounting
 Behavioral economic index of impulsivity
 Delay discounting refers to the amount that a reward is
discounted based on its delay in time
 Smaller-Sooner vs. Larger-Later Preference
 Delay Discounting Task
 Would you rather have $1 today or $100 in 7 days?
 Points of indifference gathered across time periods
 Temporal Discounting Function(s):
V = A/(1 + kD)
Ainslie, 1975; Bickel & Marsh, 2000; Mazur, 1987; Rachlin & Green, 1972; Reynolds, 2006
Temporal Discounting Function
$100
Subjective Value
$80
$60
$40
$20
$0
0
20
40
60
Delay in Days
80
100
Temporal Discounting Function
$100
Subjective Value
$80
$60
$40
$20
$0
0
20
40
60
Delay in Days
80
100
Relative Level of Impulsivity
Impulsive Discounting, Addictive Disorders and
Other Psychiatric Disorders
Delay Discounting and AUD Severity
MacKillop et al., 2010
Findings from Categorical Designs
Bickel et al., 1999; Coffey et al., 2003; MacKillop et al., 2010; Madden et al., 1997; Petry, 2000
Impulsive Discounting and ADHD
Paloyelis et al., 2010
Impulsive Discounting among Individuals
with Schizophrenia and Bipolar Disorder
Ahn et al., 2011
Impulsive Discounting and Dysregulated
Eating
Mole et al., 2014
Impulsive Discounting and Dysregulated
Eating
Petry et al., 2002
Recapitulation
 Impulsive delay discounting:
 Robustly associated with addictive disorders
 Increasingly linked to antisociality, ADHD, schizophrenia,
bipolar disorder, and dysregulated eating
 Not linked to internalizing disorders and significantly
lower among individuals with anorexia nervosa
 Theorized to be a core process in self-regulation failure in these
disorders
Brain Imaging and
Clinical Applications
Neural Basis of Impulsive Delay Discounting
Amlung...MacKillop (2012) Addiction Biology
Neural Basis of Impulsive Delay Discounting
ACC-SMA Axis of Conflict
Amlung…MacKillop (2012) Addiction Biology
Discounting and Smoking Cessation
 Impulsivity is inversely associated with days to smoking lapse
MacKillop & Kahler , 2009
Discounting and Smoking Cessation
 Impulsivity is inversely associated with days to smoking lapse
MacKillop & Kahler, 2009
Discounting and Treatment Response
Study
Condition
Tucker et al. (2002)
Alcohol dependence
Tucker et al. (2006)
Alcohol dependence
MacKillop & Kahler (2007)
Nicotine dependence
Krishnan-Sarin et al. (2007)
Nicotine dependence
Yoon et al. (2007)
Nicotine dependence
Tucker et al. (2008)
Alcohol dependence
Passetti et al. (2011)
Opiate Dependence
Washio et al. (2011)
Cocaine dependence
Stanger et al. (2012)
Marijuana abuse
Sheffer et al. (2012)
Nicotine dependence
Best et al. (2012)
Obesity
Peters et al. (2013)*
Marijuana Dependence
Sheffer et al. (2014)
Nicotine Dependence
What’s Next?
 Integrating brain imaging with smoking cessation
treatment
 What forms of neural activity predict whether a person will
be able to quit smoking?
 Impulsive discounting as a treatment target
 If we reduce impulsive discounting, can we improve
treatment response?
 Episodic future thinking and working memory training
show particular promise
 Genetic influences on impulsive discounting (but that’s a
whole other presentation)
Acknowledgments

National Institute on Drug Abuse
 P30 DA027827 (Brody)
 R01 DA 032015 (de Wit)
 R21 DA031269 (Sweet)
 R01 DA028188 (Eby)
 R01 DA034739 (Obasi)

National Institute on Alcohol Abuse and Alcoholism
 K23 AA016936 (MacKillop)
 R21 AA017696 (MacKillop)
 R13AA02285801 (MacKillop)
 R01AA018129 (Cook)





National Heart, Lung, and Blood Institute - R21 HL113742-01 (Schmidt)
National Center for Responsible Gaming (Goodie)
Alcoholic Beverage Medical Research Foundation (MacKillop)
Global Research Advances in Nicotine Dependence (MacKillop)
Robert Wood Johnson Foundation (MacKillop)
NO PRIVATE INDUSTRY
CONFLICTS OF INTEREST
Acknowledgments
Acknowledgments
Thank You